This invention relates to an apparatus for moving a vehicle having one or more wheels or wheel assemblies on a predetermined surface and, more particularly, to an apparatus which is adapted to move such a vehicle by rotating at least one wheel of the vehicle through an element functionally engaging the wheel periphery.
There are many situations where a heavy wheeled vehicle such as an airplane, trailer, or railway car must be moved for short distances on a surface such as land, road, and an airfield runway, the floor of a building, a railway track or the like through use of some sort of auxiliary towing apparatus. In such situations, it is frequently not possible or not economic to use the engines of the vehicle itself or the normal towing mechanism for the vehicle, such a truck rig or locomotive, to move the vehicle either because of the position or maneuvering requirements of the vehicle or because the fuel expended by the normal drive mechanism would be far greater than the existing moving requirements require.
An example of the type of situation indicated above is the moving of an aircraft on the ground either into or from a hanger for repair or storage or between the loading ramp and a runway for takeoff or landing. Particularly for large jet aircraft, and particularly where the aircraft must wait for some period of time after it starts moving to the runway before it is cleared for takeoff, using the airplane's engines to move the aircraft on the ground uses a significant amount of fuel. It also requires that the aircraft's brakes be used to stop the aircraft and to control the speed of the aircraft against the thrust of the jet engines, causing wear on the aircraft brakes.
To overcome the above problems, towing tractors have been heretofore used to move aircraft on airfield runways and ramps. However, since modern aircraft becoming increasingly heavy, the towing tractors must also be made larger and heavier in order to be able to achieve sufficient traction to be able to tow heavy aircraft. These vehicles also require large wheels to achieve traction, efficient brakes, and heavy axles. As the size of these vehicles have increased, they have become increasingly expensive and clumsy. In addition, additional personnel has been required to attach the towing bars of such tractors to the aircraft as well as to operate the tractor, further increasing the cost of using such vehicles.
Attempts have been made to replace the towing tractors with smaller, more maneuverable, and easier to operate moving apparatus which are adapted to make driving frictional contact with the peripheral surface of at least of one of the aircraft landing wheels to cause rotation of the landing wheels and thus movement of the aircraft. With such apparatus, the weight of the aircraft itself provides the required ground traction so that relatively small and easily maneuverable apparatus may be utilized. Examples of the devices of this type are shown in U.S. Pat. Nos. 2,997,121; 3,005,510; 3,025,922 and 3,150,734. However, devices of the type described in these patents have not come into general use because they have limitations as to the type of aircraft wheels which they can be attached to and cannot be used universally with any type of aircraft. For example, the apparatus described in U.S. Pat. No. 3,005,510 can only be attached to the landing gear of an airplane that has its landing wheels arranged as a bogie, with at least two wheels within certain predetermined distances from each other. The moving apparatus can then be placed between and adjusted to make frictional contact with both wheels. This apparatus cannot for example be used with the nose wheel of an aircraft which has only a single wheel or a pair of wheels which are coaxial.
While the apparatus described in the other U.S. Patents indicated above can be attached to a landing gear that has a single wheel, these apparatus must be locked to the ends of the axle of a wheel of a aircraft to enable their drive roller to be pressed against the aircraft wheel. Since the wheels of aircrafts are of many sizes and widths, and as the construction of their axles vary greatly, it is not possible to construct an apparatus of the type described in these patents which would be usable with all aircraft.